I am new to Animate CC and I just wanted to try a small animation. I created a rectangular.

When I want to select it with the selection tool by not making the selection all over the object but touching it partially as I usually do in all other Adobe applications, the selection tool cuts my object where the frame of this tool hits my object. So I have two rectangulars on the layer. Or a new one and the old one missing this new created piece.

Do I unterstand something totally wrong? It does not make sense to me, since it's the selection tool which should select an object and not parts by splitting it.

the selection tool will select all of the shape you click on. you can also press and drag the selection tool to select multiple shapes or the rectangular part of a shape selected by dragging. and you can use the lasso/polygon tool to select parts of shapes (and there are other ways to make selections/subselections).

thanks for taking a look at my post. Maybe I mis-explained the behavior. I've uploaded a screencast. I think this is not what the selection tool should do, should it? The lasso, yes. I'm massively irritated. Working with Illustrator since a lot of years.

yes, that's working exactly as expected and as explained in my first post: you can also press and drag the selection tool to select multiple shapes or the rectangular part of a shape selected by dragging

if you want to select an entire shape click on it, don't drag. if you want to select a shape and adjoining shapes (eg, a shape and its stroke/boundary) double click it.

When I want to select it with the selection tool by not making the selection all over the object but touching it partially as I usually do in all other Adobe applications, the selection tool cuts my object where the frame of this tool hits my object

That's exactly how the rectangular selection tool works in Photoshop, an Adobe product.

And, that's happening because they're not objects, they're shapes. If you want your shapes to be treated as objects, you have to turn on object drawing mode, or group the shape after it's drawn.